The invention is related to a method and illustration device for the register mark setting for printing presses for multicolor printing.
With multicolor printing in the printing industry, individual successive printing modules in the printing press are used to generate various color separations. In the printing modules, the generated color separations are applied successively on print stock and, after having been printed on top of one another, produce the ultimate colored print image. In order to guarantee a precisely superposed printing or superposition of the color separations and a flawless print image, register marks (which are also referred to as registers for multicolor printing) are printed on print stock or conveyor belt or web during calibration runs for preparation of the actual printing process. During the calibration runs a number of register marks are applied to the web, for example, and subsequently, the proper positioning of these register marks is checked. Sometimes pulse counters are used to control the points in time, at which the register marks are applied to the web by a printing drum or a sub-carrier, or by a rubber-covered drum between the printing drum and the print stock. In a particular concept that uses calibration runs, first the registration marks are established with a first calibration run that sets the distances between the frames. Thereafter a second calibration run establishes the distances between the individual register marks of a single large frame, as well as the same color separations from one another, e.g., the distance of the register mark for magenta of a large frame to the subsequent register mark for magenta.
Frames of register marks are composed of a defined constant number of several individual register marks for individual color separations printed close together. There is a given distance between the frames of the register marks; often with the first calibration run, a frame is used for every simulated sheet of a stock. In contrast to the above-mentioned, a large frame contains all the register marks of the calibration run and has a precise beginning and end. A pulse counter generates the printing on the web during the calibration at the appropriate time, so that the register marks are applied to the web in time. The register marks are applied at similar distances, which are determined by a given number of pulses per time in relationship to the speed, which occurs during the printing of the web with register marks according to the emission of a triggering signal. This speed is basically determined according to the speed of the motor-driven web and by the friction driven related printing drum and the sub-carrier or separation drum. The individual register marks are thus applied to the web with constant pulses. The term xe2x80x9clinexe2x80x9d is defined by an arranged series of pixels that are transverse to the described surface, stock or web; the term xe2x80x9careaxe2x80x9d defines a plurality of lines. In the subsequent printing, the shifting of the register marks leads to shifts of the superposed color separations.
This concept is used for a printing press to provide a perfect distance between the frames of register marks within a tolerance, from which flawless beginnings of images of the individual color separations follow. Also, its purpose is to provide flawless distances between the register marks of the same color on the web, with which color shifts of areas or lines within the print image are prevented. To fulfill both requirements, as described, two individual calibration runs are required, with the first calibration run for calibrating the frames and a second calibration run for calibrating the individual register marks of the same color. Furthermore, there is a problem that the longer the calibration process lasts, the greater the effect of other errors, i.e., the effectiveness of the calibration process is reduced.
In view of the above, it is the purpose of this of the invention to provide registerability with a single calibration run. The invention advantageously solves the task by using a calibration run to calibrate a register frame and the correction data produced is used to calibrate the registerability of individual areas or individual lines of color separations from printing modules of the printing press, whereby the data of the register marks are detected to determine the correction data and are set in relationship to positions of an illustration drum and/or of a separation drum of said printing press.
The invention, and its objects and advantages, will become more apparent in the detailed description of the preferred embodiment presented below.